github.com/m3db/m3@v1.5.0/src/x/serialize/decoder_fast.go (about)

     1  // Copyright (c) 2020 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
     6  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package serialize
    22  
    23  import (
    24  	"bytes"
    25  	"fmt"
    26  )
    27  
    28  // TagValueFromEncodedTagsFast returns a tag from a set of encoded tags without
    29  // any pooling required.
    30  func TagValueFromEncodedTagsFast(
    31  	encodedTags []byte,
    32  	tagName []byte,
    33  ) ([]byte, bool, error) {
    34  	total := len(encodedTags)
    35  	if total < 4 {
    36  		return nil, false, fmt.Errorf(
    37  			"encoded tags too short: size=%d, need=%d", total, 4)
    38  	}
    39  
    40  	header := ByteOrder.Uint16(encodedTags[:2])
    41  	encodedTags = encodedTags[2:]
    42  	if header != HeaderMagicNumber {
    43  		return nil, false, ErrIncorrectHeader
    44  	}
    45  
    46  	length := int(ByteOrder.Uint16(encodedTags[:2]))
    47  	encodedTags = encodedTags[2:]
    48  
    49  	for i := 0; i < length; i++ {
    50  		if len(encodedTags) < 2 {
    51  			return nil, false, fmt.Errorf("missing size for tag name: index=%d", i)
    52  		}
    53  		numBytesName := int(ByteOrder.Uint16(encodedTags[:2]))
    54  		if numBytesName == 0 {
    55  			return nil, false, ErrEmptyTagNameLiteral
    56  		}
    57  		encodedTags = encodedTags[2:]
    58  
    59  		bytesName := encodedTags[:numBytesName]
    60  		encodedTags = encodedTags[numBytesName:]
    61  
    62  		if len(encodedTags) < 2 {
    63  			return nil, false, fmt.Errorf("missing size for tag value: index=%d", i)
    64  		}
    65  
    66  		numBytesValue := int(ByteOrder.Uint16(encodedTags[:2]))
    67  		encodedTags = encodedTags[2:]
    68  
    69  		bytesValue := encodedTags[:numBytesValue]
    70  		encodedTags = encodedTags[numBytesValue:]
    71  
    72  		if bytes.Equal(bytesName, tagName) {
    73  			return bytesValue, true, nil
    74  		}
    75  	}
    76  
    77  	return nil, false, nil
    78  }